Briefcases the only solution?

Surely there are many occasions when you need to transport a bunch of manila folders? Is the briefcase the only solution?

I'm renowned for being mega oragnised and mega scrappy. The nice way of putting it, is I'm 'hard on things' (as Jolly said the other day). This means I treat things badly. There's always a coffee ring or a crack or a dogear within a day or two with me.

So I finally got round to trying to find a way of protecting my manila folders when I trasported them in my backpack or satchel (old school, punkrcok canvas bag, thank you very much, not some nasty Krumpler man bag).

It was amazingly hard to find hard, protective manila-folder sized folders. I found one. It's now cracking (I'm hard on things you see). So I need another. It's gonna be a hunt again.

Do I need to buy a special briefcase backpack? Is that what normal people who transport manila folders and ride bikes do? Does anyone know the answer to this?

How do grownups do this?